Widespread Thunderstorms Possible Wed – Friday Morning

Home / Uncategorized / Widespread Thunderstorms Possible Wed – Friday Morning

A couple more surges/kinks in the ridge will send plumes of significant sub-tropical/monsoonal moisture into northern California over the next couple of days… peaking over the next couple of days.

Tonight's IR satellite, radar, 300mb heights, and metars indicating the center of the ultra-strong ridge just off to our east.

Tonight’s IR satellite, radar, 300mb heights, and metars indicating the center of the ultra-strong ridge just off to our east.

Wednesday…

Precipitable water values in excess of 1.2″ combined with very strong surface heating will support strong instability over the mountains once again… with surface CAPEs potentially exceeding 3,000j/kg in some locations… and MLCAPEs in the 1000 – 2000j/kg range, all of which is fairly significant our standards. Compared to earlier in the week, the valley capping inversion won’t be as strong, but it will still be fairly strong… with surface CIN values still in the -100 – 200j/kg range from around Yuba City southward. In the northern valley, the cap won’t be as strong… perhaps below -75j/kg which is more supportive of some elevated convection. Though the best chance of valley storms would be in the north valley due to the lack of a stronger cap, there is still a slight chance of a storm (or a few if things pan out) in other parts of the valley). Overnight, elevated instability shifts farther south over the southern Sacramento and northern SJ valley, east and westward horizontally. This is where the best chance of nocturnal convection will be.

Thursday…

Instability isn’t as strong as it was Wednesday… with SBCAPEs in the 1000 – 2000j/kg range andth MLCAPEs also in the same general range. What will make up for the slightly weaker instability will be the decrease in the capping inversion, with CIN values forecasted to generally be under 100j/kg in the valley. Models aren’t in good agreement with the amount of convection that develops Thursday. Some models indicate Thursday being more active than Wednesday, while others indicate Thursday being less active than Wednesday. The GFS and ECMWF indicate Thursday being much more active, while the NAM is much dryer. Since the GFS and ECMWF are usually more accurate than the NAM, I’d preferably lean with these solutions rather than the NAM’s. In this case, Thursday could end up being the most active day out of the last several days, including the best chance of storms in the valley. If the GFS and ECMWF are indeed correct, nocturnal thunderstorms could continue into the morning hours of Friday.

Thunderstorm threats…

Given the fairly moist airmass (precipitable water values on average around 1.2 – 1.4″ and dew points in the 50s and 60s), moderately unstable air, and somewhat steep lapse rates, hail, possibly severe in some cases is possible, along with strong winds from downbursts and outflow (some of which could also be considered severe), extremely heavy rainfall due to slow storm motions (generally between 5 and 15kts) which could cause flooding and mud/rock/landslides as seen along I-80 and Highway 70 in the mountains Tuesday, and copious amounts of lightning given the decent instability and elevated nature of the thunderstorms (which seem to have more lightning than cold pool convection like we normally see in the winter months).

Graphic indicating chance regions and the placement of the ridge, along with thunderstorm threats.

Graphic indicating chance regions and the placement of the ridge, along with thunderstorm threats.

We’ll see what happens, and if another update is needed due to model changes one shall be posted. Stay tuned!

Comments
  • wxtracker15

    Thunderstorms are a little more spread apart today (Wednesday) compared to Tuesday, however storms are more organized today given the strong instability and pockets of decent effective shear (20 – 35kts). A few severe storms have developed so far which have been capable of large hail and damaging winds. Threat should continue until 8pm or so before turning into more of a isolated nocturnal thunderstorm type deal.

    Radar/satellite/metars as of 3:50pm: http://images.norcalweather.net/albums/radar/489.png

Leave a Reply to wxtracker15 Cancel reply

%d bloggers like this: